The present invention relates to an apparatus for ABS-integrated brake pad wear indication in a motor vehicle in which a central ABS or ABS/ASR microcomputer is supplied with wheel speed signals and brake pad wear signals from wheel sensors, devices for indicating fault states and/or brake pad wear such that, at least wheel by wheel, lines which transmit wheel speed signals and brake pad wear signals to the microcomputer are combined or laid in a single strand, are fixed and, if necessary, plugged in.
With only slight modifications, a conventional practicable implementation of brake pad wear indicators in passenger vehicles is performed for example in accordance with FIG. 3. Speed sensor lines 3.1 to 3.4 of wheel speed sensors 1.1 to 1.4 connect to an ABS or ABS/ASR control unit 8 in a plurality of plug-in connectors 7.1, 7.2 and 7.3. Brake wear sensor lines 4.1 to 4.4 of wheel brake pad wear sensors 2.1 to 2.4 connect to the instrument cluster 6 in the dashboard of the vehicle via a connector 5xe2x80x2 or directly on the plug-in connector 5 to drive a warning display integrated there before or upon pad wear-out. Over their length, the aforementioned individual lines are provided with individual, respectively doubled plug-in connectors 14xe2x80x2, 15xe2x80x2, 16xe2x80x2 and 17xe2x80x2. Other electrical connections 10a and 10b are provided between the ABS or ABS/ASR control unit 8 and the instrument cluster 6 for the purpose, inter alia, of permitting a plurality of warning displays in the instrument cluster 6 in the event of an error in ABS, ASR and otherwise. The lines 3.1 to 3.4, 4.1 to 4.4 and 10a, 10b are led individually via or through holders and, provided in duplicate in each case, grommets 19xe2x80x2, and fixed.
This conventional approach is expensive and is susceptible to high electromagnetic compatibility (EMC) interference during operation of radio telephones in or in the vicinity of vehicles so equipped.
DE 26 06 012 A1 describes a sensor arrangement for an antiblock device for vehicle brakes, in which the pulse generator sampling the wheel speed is electrically connected to the sampling circuit of a brake pad wear indicator. Using this arrangement, a wheel speed signal and a brake pad wear signal are transmitted from a wheel to the corresponding control unit via the same two wires of a single line.
DE 34 33 254 A1 describes a device for testing the serviceability of a slip-controlled brake system. In this system, all the lines which come from the wheels and transmit wheel speed signals and/or control signals are led to a plug-in connector which is normally connected to the control unit for the purpose of slip-controlled vehicle braking.
DE 38 29 949 A1 discloses, inter alia, a control device for operating an electric hydraulic service brake device in a motor vehicle. It comprises an electronic ABS control unit which processes individual wheel speed signals and other inputs for the purpose, inter alia, also of receiving and of processing signals from brake pad wear transmitters on braked wheels. Signal lines from sensors near the wheels lead to the central control unit.
An object of the invention is to provide an improved device for ABS-integrated brake pad wear indication in a motor vehicle, which device has a high electromagnetic compatibility (EMC), but is nevertheless cost effective.
This object has been achieved in accordance with the present invention by a device in which lines combined or laid in a single strand, wheel by wheel are connected with a single terminal plug-in connector of a brake control unit containing the microcomputer. An instrument cluster is arranged in a vehicle dashboard and associated with said devices for indicating at least one of fault states and wear, with reference to their drive. The instrument cluster is connected to the brake control unit via only a single signal path which leads via a single terminal plug-in connector, and state and/or warning signals are transmittable from the brake control unit by one of pulse width modulation and per protocol to the instrument cluster which comprises at least one dedicated microcomputer which performs one of the pulse width demodulation and protocol demodulation and driving of associated displays.
The device according to the present invention has the advantage that, in conjunction with a simultaneous cost reduction, there is a substantial suppression of EMC interference without the need for appreciable structural modifications to known ABS or ABS/ASR control units. A high EMC interference suppression is achieved essentially by constructing all the line paths with simultaneous avoidance of current loops and induction surfaces. In addition, the wheel speed and pad wear signal lines are respectively fed to the ABS or ABS/ASR control unit in a single strand or combined at least via common fixings, grommets, intermediate connecting plugs and a single terminal connecting plug. Owing to coding of different warning signals for, e.g., ABS, ASR and brake pad wear, the connection between the ABS or ABS/ASR control unit and the instrument cluster is reduced to a single line.